Env filter trap fault

[deepak0414]

This PR adds following

• encodings.h: CSR and bit definitions (in existing and new CSRs) for Zisslpcfi extension [1]
• Delegates illegal instr exception: In vm environment delegates illegal instr exception because Zisslpcfi uses illegal instruction to report cfi violations to M/S mode.
• adds support for trap filtering: Certain traps needs to be filtered by test by test basis and currently there is no such support in env. This patch allows test case authors to implement FILTER_TRAP macro and allow certain traps to go back to test cases.
  • adds support for page fault filtering: Certain page faults needs to be filtered by test by test basis and currently there is no such support in env. This patch allows test case authors to implement FILTER_PAGE_FAULT macro and allow certain page faults to go back to test cases.
  • page fault filters can provide which new encodings to use and whether to copy the page or not.

[1] - https://github.com/riscv/riscv-cfi

[aswaterman]

I would like to wait to merge this PR until the CFI extension is closer to being frozen. It seems likely to change in the interim.

Also, please remove all of the debugging code that was added.

[deepak0414]

@aswaterman would you be open to adding trap filtering and page fault filtering. I can make a PR just for that.

That change is anyways seems like can be used by tests for other arch extensions.

[aswaterman]

Seems reasonable; send me a new PR and let’s talk about it there.